RDTs are diagnostic assays designed for use at the point-of-care. RDTs are generally low cost, relatively simple to operate and read, stable at a variety of operating conditions, and work in a relatively short period of time. Although the use of RDTs is not so limited, RDTs have particular application in low-resource settings where local conditions do not provide technology, equipment, and training for more complicated laboratory testing. Moreover, many patients may not reside near or cannot travel to medical sites where such testing is available.
RDTs are thus very useful tools to screen infectious diseases in resource limited settings or remote locations where conventional approaches (e.g., clinical examination, microscopy, etc.) are extremely limited or even not available. Penetration of RDT technologies to public health endeavors has generated several advantages including, but not limited to, better patient management where the infection symptoms are not specific to a particular disease (i.e., asymptomatic diseases), outbreak surveillance in high-risk endemic areas, and wide-spread health care delivery by minimally trained technicians.
A variety of types of RDTs are in existence. These include, by way of example, lateral flow tests (immunochromatographic strip tests), agglutination tests, flow-through tests, and solid-phase (dipstick) assays. Lateral flow tests are one of the most common types of RDT and include all the reactants and detection functionality included within a test strip. In a lateral flow test, the strip is placed into a sample and the results are read after a certain amount of time has elapsed. An example of a lateral flow test is commonly used home pregnancy tests. An agglutination RDT works by observing the binding of particles to a target analyte which is observed through the naked eye or through a microscope. In a solid phase RDT, a dipstick is placed into contact with a sample and then washed and incubated to prevent non-specific analyte blinding. This test requires several steps such as washing and thus requires some degree of training. These limitations can limit the usefulness of such tests in resource-limited settings. Flow through tests obtain results quicker than lateral flow tests but require buffer solutions and additional wash steps that can limit portability and usefulness.
RDTs are used to test for the presence of infectious disease. For example, RDTs are used to detect HIV, malaria, syphilis, and Hepatitis B. RDTs can also be used to detect other biomarkers or physical conditions. For example, RDTs are used in making fertility determinations. RDTs can also be used to test blood sugar and cholesterol levels.
Meanwhile, the current and expanding universe of wireless communication technology exhibits promising potential to be utilized for powerful wireless health applications even in the least developed parts of the world. With more than 5 billion subscriptions worldwide, mobile phones can be potentially used for sensing, screening and transferring ubiquitous health related data using already embedded components (i.e., CMOS/CCD sensors, LCD displays, WIFI/GSM/GPS receivers/transmitters, Bluetooth, etc.) even in field settings. Therefore, wireless communication technology remains an exciting opportunity to transform the fight against epidemics, opening new gates towards cloud-based outbreak monitoring platforms.
Attempts have been made at integrating mobile phones with diagnostic testing functionality. For example, Breslauer et al. have proposed a brightfield and fluorescent imaging system that includes a bulky attachment that is used in connection with a commercially available mobile phone. Breslauer et al., Mobile Phone Based Clinical Microscopy for Global Health Applications, PLOS One, www.plosone.org, Vol. 4, Issue 7 (2009). Smeared samples of malaria-infected cells and sickle cell anemia samples were imaged with the camera. These images were then transferred to a separate laptop computer for automated counting of cells. In another example, Tuijn et al. discloses a system whereby mobile phones are secured to a standard (and bulky) light microscope to capture images on a mobile phone. These images are then transferred to a central database for assessment, feedback, and educational purposes. Tuijn et al., Data and Image Transfer Using Mobile Phones to Strengthen Microscopy-Based Diagnostic Services in Low and Middle Income Country Laboratories, PLOS One, www.plosone.org, Vol. 6, Issue 12, (2011). Roche et al. have used a camera phone for applying localized surface plasmon resonance (LSPR) label-free sensing that uses gold nanoparticles and nanorods in an assay solution contained in a in a cuvette affixed to the mobile phone. Images obtained from the camera were then offloaded to a separate computer for image processing.